I normally increase it by larger amounts at first (but this is AMD cards) then start going by smaller increments until I find the limit. After I find the limit I normally back it down (depending on the OC if it's only slight, which I think you'll be in) maybe 10-20). It seems for some searches that you won't get past 1000 mhz so I'd just aim for 980-990.

Memory largely depends on the type used (each manufacturer chooses) but if it's about 4100 stock (might show up as 820 because GDDR5 is a base value of 820 x 5 = 4100) I'd try for 4500 (or 900).